1. Field of the Invention
The invention concerns a system for the in situ checking of turbine engine blades by eddy currents, the system including a unit for positioning the detection probe on the airfoil portion to be checked.
2. Description of the Prior Art
The rupture of a turbine engine blade generally leads to considerable damage. It is therefore important to be able to detect any metallurgical or physical structural defect, not only on the surface but internally. The use of eddy currents, in a known manner, offers this possibility and, with the aid of a probe moved over the surface of the blade, makes it possible to determine the existence and location of the defects.
The position of the probe in relation to the surface explored is an important factor in the precision of the results, and a system making it possible to fix this factor was described at the Federal Aeronautical Agency's symposium on reliability, held in Washington, D.C. on Nov. 18, 1965. That system is composed of a positioning unit, the shape of which matches that of the airfoil portion of the blade, pierced by five ports into which a check probe may successively be positioned. This unit thus perfectly locates the position of the probe in relation to the surface, but has the drawback of not allowing the checking of discrete areas. This point-by-point measurement technique has the drawback of not detecting small defects located between the measurement points.
This problem can be alleviated by equipping the probe with a stop and manually moving the unit in contact with the edge of the airfoil portion. The need for qualified, well-trained personnel in the use of this technique, however, makes it impossible to fully eliminate the difficulties of manual, in situ exploration due to the smallness of the space and, consequently, the reliability of the measurements is not very good.